As Shan says you shouldn’t really be storing passwords yourself in a dataset as it would make it easier for people to try to obtain them and then gain access to members data etc, you would be liable for any data breach and not Wix.
If you are trying to pre-approve members then you can’t do that currently, although you can vote for the request here.
https://support.wix.com/en/article/request-pre-approving-site-members
You can try this workaround that was posted on Stack and see if it is still viable, however it would still require all the members to do their own password again.
https://stackoverflow.com/questions/53181905/workaround-to-import-users-as-site-members-on-wix-com
So to be honest, you would be much easier just asking them to sign themselves up on your site.